There has been another chemical leak at Orica's Newcastle plant within an hour of the Environment Protection Authority (EPA) confirming it had started legal action against the company.

The EPA is taking action against Orica over the hexavalent chromium leak at its ammonia plant in August that outraged in the Newcastle community.

"The EPA alleges that Orica breached its environment protection licence in that it failed to operate its ammonia plant in a proper and efficient manner," EPA spokesman Greg Sullivan said in a statement.

"The EPA also alleges that Orica failed to notify the EPA as soon as practicable after becoming aware of the incident and to provide all relevant information to the EPA about the incident.

"Orica has a duty of care to the people of Newcastle and the response from Orica immediately after the incident was not satisfactory."

Six fire units and the Hazardous Materials Unit were called to the Kooragang Island plant in response to the leak.

Two men have been hospitalised after the leak.

Superintendent Paul Bailey from Fire and Rescue says the men were working outside in a rail yard when they had difficulty breathing.

"On arrival two railway depot workers were found to be mildly affected by a gas. Fire brigade undertook some testing and found the gas to be ammonia," he said.

Orica told residents there were no safety risks after ammonia was released three times over a 45 minute period.

A Fire and Rescue NSW spokesman said the problem had been tracked to a pressure release valve but there have been no evacuations.

The first spill outraged the community, which was only told about the spill several days after it happened.

The incident led to a tightening of NSW's pollution laws, including new rules forcing companies to report pollution breaches immediately or face a fine of up to $2 million.

You have no doubt been hearing a lot about the Paris Agreement and know that it pertains to climate change, but are too embarrassed at this stage to ask for an overall explanation of what it's all about.